/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.optimize.evaluation;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.*;
import proguard.classfile.constant.*;
import proguard.classfile.editor.*;
import proguard.classfile.instruction.*;
import proguard.classfile.instruction.visitor.InstructionVisitor;
import proguard.classfile.util.SimplifiedVisitor;
import proguard.classfile.visitor.*;
import proguard.optimize.info.SimpleEnumMarker;
import proguard.optimize.peephole.*;

/**
 * This ClassVisitor simplifies the classes that it visits to simple enums.
 *
 * @see SimpleEnumMarker
 * @see MemberReferenceFixer
 * @author Eric Lafortune
 */
public class SimpleEnumClassSimplifier extends SimplifiedVisitor
    implements ClassVisitor, AttributeVisitor, InstructionVisitor {
    // *
    private static final boolean DEBUG = false;
    /*/
    private static       boolean DEBUG = System.getProperty("enum") != null;
    //*/

    private static final int ENUM_CLASS_NAME = InstructionSequenceReplacer.A;
    private static final int ENUM_TYPE_NAME = InstructionSequenceReplacer.B;
    private static final int ENUM_CONSTANT_NAME = InstructionSequenceReplacer.X;
    private static final int ENUM_CONSTANT_ORDINAL = InstructionSequenceReplacer.Y;
    private static final int ENUM_CONSTANT_FIELD_NAME = InstructionSequenceReplacer.Z;

    private static final int STRING_ENUM_CONSTANT_NAME = 0;

    private static final int METHOD_ENUM_INIT = 1;
    private static final int FIELD_ENUM_CONSTANT = 2;

    private static final int CLASS_ENUM = 3;

    private static final int NAME_AND_TYPE_ENUM_INIT = 4;
    private static final int NAME_AND_TYPE_ENUM_CONSTANT = 5;

    private static final int UTF8_INIT = 6;
    private static final int UTF8_STRING_I = 7;

    private static final Constant[] CONSTANTS = new Constant[] {new StringConstant(ENUM_CONSTANT_NAME, null, null),

        new MethodrefConstant(CLASS_ENUM, NAME_AND_TYPE_ENUM_INIT, null, null),
        new FieldrefConstant(CLASS_ENUM, NAME_AND_TYPE_ENUM_CONSTANT, null, null),

        new ClassConstant(ENUM_CLASS_NAME, null),

        new NameAndTypeConstant(UTF8_INIT, UTF8_STRING_I),
        new NameAndTypeConstant(ENUM_CONSTANT_FIELD_NAME, ENUM_TYPE_NAME),

        new Utf8Constant(ClassConstants.METHOD_NAME_INIT), new Utf8Constant(ClassConstants.METHOD_TYPE_INIT_ENUM),};

    private static final Instruction[][][] INSTRUCTION_SEQUENCES = new Instruction[][][] {{
        // Replace new Enum("name", constant)
        // by constant + 1.
        {new ConstantInstruction(InstructionConstants.OP_NEW, CLASS_ENUM),
            new SimpleInstruction(InstructionConstants.OP_DUP),
            new ConstantInstruction(InstructionConstants.OP_LDC, STRING_ENUM_CONSTANT_NAME),
            new SimpleInstruction(InstructionConstants.OP_ICONST_0, ENUM_CONSTANT_ORDINAL),
            new ConstantInstruction(InstructionConstants.OP_INVOKESPECIAL, METHOD_ENUM_INIT),},
        {new SimpleInstruction(InstructionConstants.OP_SIPUSH, ENUM_CONSTANT_ORDINAL),
            new SimpleInstruction(InstructionConstants.OP_ICONST_1),
            new SimpleInstruction(InstructionConstants.OP_IADD),}},
        {
            // The name constants may have been encrypted.
            // Replace <init>(..., constant)
            // by <init>(..., 0); pop; constant + 1.
            {new SimpleInstruction(InstructionConstants.OP_ICONST_0, ENUM_CONSTANT_ORDINAL),
                new ConstantInstruction(InstructionConstants.OP_INVOKESPECIAL, METHOD_ENUM_INIT),},
            {new SimpleInstruction(InstructionConstants.OP_ICONST_0),
                new ConstantInstruction(InstructionConstants.OP_INVOKESPECIAL, METHOD_ENUM_INIT),
                new SimpleInstruction(InstructionConstants.OP_POP),
                new SimpleInstruction(InstructionConstants.OP_SIPUSH, ENUM_CONSTANT_ORDINAL),
                new SimpleInstruction(InstructionConstants.OP_ICONST_1),
                new SimpleInstruction(InstructionConstants.OP_IADD),}},};

    private final CodeAttributeEditor codeAttributeEditor = new CodeAttributeEditor(true, true);

    private final InstructionSequencesReplacer instructionSequenceReplacer =
        new InstructionSequencesReplacer(CONSTANTS, INSTRUCTION_SEQUENCES, null, codeAttributeEditor);

    private final MemberVisitor initializerSimplifier = new AllAttributeVisitor(this);

    // Implementations for ClassVisitor.

    public void visitProgramClass(ProgramClass programClass) {
        if (DEBUG) {
            System.out.println("SimpleEnumClassSimplifier: [" + programClass.getName() + "]");
        }

        // Unmark the class as an enum.
        programClass.u2accessFlags &= ~ClassConstants.ACC_ENUM;

        // Remove the valueOf method, if present.
        Method valueOfMethod = programClass.findMethod(ClassConstants.METHOD_NAME_VALUEOF, null);
        if (valueOfMethod != null) {
            new ClassEditor(programClass).removeMethod(valueOfMethod);
        }

        // Simplify the static initializer.
        programClass.methodAccept(ClassConstants.METHOD_NAME_CLINIT, ClassConstants.METHOD_TYPE_CLINIT,
            initializerSimplifier);
    }

    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitCodeAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute) {
        // Set up the code attribute editor.
        codeAttributeEditor.reset(codeAttribute.u4codeLength);

        // Find the peephole changes.
        codeAttribute.instructionsAccept(clazz, method, instructionSequenceReplacer);

        // Apply the peephole changes.
        codeAttributeEditor.visitCodeAttribute(clazz, method, codeAttribute);
    }
}
